backend/main.py

import os
import logging
from contextlib import asynccontextmanager
from fastapi import FastAPI, Request
from fastapi.middleware.cors import CORSMiddleware
from fastapi.staticfiles import StaticFiles
from qdrant_client import QdrantClient
from qdrant_client.models import Distance, VectorParams, PayloadSchemaType

from src.config import get_settings
from src.models import JobDescription, Candidate, MatchResult, Session
from src.routers import jds, candidates, matching, sessions, admin

# Configure root logger so ALL module loggers (stage2, reranker, etc.)
# emit to stdout — critical for error visibility on Hugging Face
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [%(levelname)s] %(name)s: %(message)s",
    handlers=[logging.StreamHandler()],
)

logger = logging.getLogger(__name__)
settings = get_settings()


_qdrant_client: QdrantClient | None = None
_qdrant_ready: bool = False


def get_qdrant() -> QdrantClient:
    return _qdrant_client


@asynccontextmanager
async def lifespan(app: FastAPI):
    global _qdrant_client, _qdrant_ready
    _qdrant_client = QdrantClient(url=settings.qdrant_url, api_key=settings.qdrant_api_key)

    try:
        existing = [c.name for c in _qdrant_client.get_collections().collections]
        if settings.collection_name not in existing:
            _qdrant_client.create_collection(
                collection_name=settings.collection_name,
                vectors_config=VectorParams(size=settings.vector_size, distance=Distance.COSINE),
            )
            # Create indexing for the session_id to allow fast filtering
            _qdrant_client.create_payload_index(
                collection_name=settings.collection_name,
                field_name="session_id",
                field_schema=PayloadSchemaType.UUID,
            )
            # Create indexing for years_of_experience for range filtering
            _qdrant_client.create_payload_index(
                collection_name=settings.collection_name,
                field_name="years_of_experience",
                field_schema=PayloadSchemaType.FLOAT,
            )
        _qdrant_ready = True
        logger.info("Qdrant connected — collection '%s' ready", settings.collection_name)
    except Exception as exc:
        _qdrant_ready = False
        logger.warning(
            "Qdrant unavailable at startup (%s). "
            "The API will start but vector search will fail until Qdrant is reachable.",
            exc,
        )

    app.state.qdrant = _qdrant_client
    app.state.qdrant_ready = _qdrant_ready

    # Pre-load the lightweight CrossEncoder (~80MB) eagerly at startup so the
    # first matching request doesn't pay the cold-start download cost.
    try:
        import asyncio
        from src.ml.reranker import _get_reranker
        logger.info("Warming up Neural CrossEncoder reranker...")
        await asyncio.to_thread(_get_reranker)
        logger.info("Neural CrossEncoder loaded and ready!")
    except Exception as warm_exc:
        # Log but don't crash — matching will attempt lazy-load on first request
        logger.warning(f"Reranker warm-up failed (will retry on first request): {warm_exc}")

    yield
    _qdrant_client.close()


app = FastAPI(
    title="TalentPulse — AI Candidate Matching",
    description="Two-stage retrieval + reranking pipeline for matching JDs against candidate sessions",
    version="1.0.0",
    lifespan=lifespan,
)

app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

app.include_router(sessions.router, prefix="/api/sessions", tags=["Sessions"])
app.include_router(jds.router, prefix="/api/jds", tags=["Job Descriptions"])
app.include_router(candidates.router, prefix="/api/candidates", tags=["Candidates"])
app.include_router(matching.router, prefix="/api/match", tags=["Matching"])
app.include_router(admin.router, prefix="/api/admin", tags=["Admin"])


@app.get("/health")
async def health(request: "Request"):
    qdrant_ok = getattr(request.app.state, "qdrant_ready", False)
    return {
        "status": "ok",
        "version": "1.0.0",
        "qdrant": "connected" if qdrant_ok else "unavailable",
    }


static_dir = os.path.join(os.path.dirname(__file__), "static")
if os.path.isdir(static_dir):
    app.mount("/", StaticFiles(directory=static_dir, html=True), name="static")